7 Replies Latest reply: Jun 10, 2008 2:10 PM by Matthew Knice
Király Level 6 (9,635 points)
My PRAM battery is dead. I know it's dead because my eMac's clock resets to 1969 whenever I unplug it, even for a second.

Other than the minor annoyance of resetting the clock and other PRAM info after unplugging, is there any reason to actually replace the PRAM battery? I rarely unplug the eMac anyway so I probably won't bother replacing the battery if I don't need to.

My concern is... is running the eMac with a dead PRAM battery going to damage it in some way that is not occurring to me?

eMac (1.25GHz USB 2.0), 768MB, Mac OS X (10.5.2)
  • foxberg Level 1 (125 points)
    I would just replace the battery. It's quite easy to do. I took apart a handful of these eMacs and there are instructions available on the web with photographs.
  • Király Level 6 (9,635 points)
    Yeah, but is there any negative consequence for just leaving the dead one in?

    The hassle of buying a new battery and putting it in outweigh the hassle of resetting the clock once or twice a year when I unplug the eMac. I'd just as soon not bother if I don't have to.
  • Liliana Velazco Level 1 (90 points)
    I never heard of any issues running an OS X Mac with a dead PRAM battery. As long as you're using network time the PRAM battery will be for the most part obsolete. One of the very few advantages of OS X as a matter of fact.

    However if you shall want to run OS 9 (booting to) please consider you might have nasty problems and it wont even start up.

    In which case you should restart and press Cmd X
    This will force your Mac to boot in X (providing both OS exists on the same volume)
  • JMVP Level 6 (16,840 points)
    Aside from losing any custom settings stored in PRAM (What's stored in PRAM?), a dead PRAM battery will prevent some Mac models from starting up at all, especially if they've been unplugged for a lengthy period. I don't know how much time is "lenghty" for an eMac, but I'd say the potential hassle of a dead PRAM battery outweighs the minor cost and hassle of replacing the battery.

    The PRAM battery will cost you somewhere around US$10 to $21 (figuring in tax and shipping) depending on whether bought online or at a local electronics store such as RadioShack. Instructions on replacing the battery are available at eMac - Do-It-Yourself.
  • spudnuty Level 5 (7,050 points)
    Hi Kiraly,
    My PRAM battery is dead

    Technically the term for this battery is "logic board battery" and while it does retain date and time settings it also runs the PMU which is responsible for power management. Probably still the PMU99 chip. This is from the service manual for your 1.25 (first one):
    "If the computer has a “No Power” situation, check the battery before replacing modules. A
    drained battery may be indicative of a crashed Power Management Unit.
    With the battery in the battery holder (under load), measure the voltage across the battery’s positive and ground terminals.
    Does the battery measure at least +3.5v? If not, replace the battery and reset the PMU. If the battery does measure over +3.5v, reinstall the battery and reset the PMU as above"

    I would just replace it as Foxberg and JMVP have already said. It's $4.99 (cheapest price - RS is outrageous) here at OWC plus shipping, $3 to me but I'm just across town:
    Also it's dead simple as they have said. With the access door off it's right there.

  • srojtas Level 2 (430 points)
    I would not worry about it. I have a eMac (1st Generation) myself with a dead battery and it causes no problems as long as there is a constant power source, network time on in OS 9 & X along with a internet connection, it works for me, and its been dead for 3 years. Same with my (sadly) Flower Power iMac.
  • Matthew Knice Level 1 (70 points)
    Hey Guys!
    I know what to do! go here http://eshop.macsales.com/item/Newer%20Technology/BAA36VPRAM/
    Have a good one!

    Matthew Knice